SCIENTIFIC OBJECTIVES OF AIFP

Ferroelectric materials like Poly(vinylidene fluoride) (PVDF) and its copolymer with trifluoroethylene P(VDFTrFE) are intrinsically multifunctional. In the copolymer with TrFE these ferroelectric
polymers will exhibit a Curie transition, where a phase transition between the ferroelectric and paraelectric phases occurs with increasing temperature. In the preparation of piezoelectric
polymers and copolymers it is in general necessary to apply a high poling electric field to an essentially insulating material. In the poled ferroelectric phase, these polymers exhibit relatively
high piezoelectric response and have found a broad range of applications [1, 2].

The lack of knowledge of the levels of electric fields to be applied to these polymers for their use in "active transducers" configuration, is a major obstacle to development of many applications
using these polymers in specific sensors or actuators i.e. PVDF shock sensors [3].

For "sensors" applications, piezoelectric or pyroelectric performances are based on levels of polarization under electric field applied to the sample: these levels must exceed the value of the
coercive field of the pure material to give to the material a remnant polarization. It is essential to measure the electrical induction D, the polarization P, the induction current ID, the
polarization current IP, as well as the relative permittivity versus electrical field applied to the sample. Reproducible sensors can be easily developed.

It has been found that by introducing defects into the P(VDF-TrFE) copolymers, it is possible to convert the polymer from a normal ferroelectric to a relaxor ferroelectric [4]. The class of
electroactive polymers P(VDF-TrFE-CFE) and P(VDF-TrFE-CTFE) offers unique properties in comparison with other polymers. These relaxor-ferroelectric terpolymers are multifunctional, i.e.,
electrostrictive material, dielectric for electric energy storage. High electrostrictive strain leads to large actuation capability.

One original application in liquid-filled varifocal lens on a chip has been developed by S. Choi et al. [5].

For these “relaxor” too, the knowledge of the electrical induction D, the polarization P, the induction current ID, the polarization current IP, as well as the relative permittivity versus
electrical field applied to the sample, are essential.